Pocketknives have a blade mounted to a housing, which serves both as a sheath and as a handle, for pivotable movement between sheathed and unsheathed positions. They are well known in the art as exemplified by those illustrated in U.S. Pat. Nos. 3,568,315, 4,148,140 and 4,302,877. Such knives are well suited for general purpose, occasional use while carried on a person as in men's trouser pockets and in ladies' handbags since they may assume a compact configuration with their blade safely stowed. Keys constitute another personal article that are carried in a similar manner. Typically, they are grouped as a set placed on a key ring or on an endless key chain which, for purposes of this application, is also considered to be a ring.
Heretofore, devices have been conceived for holding a key or a set of keys together with another type of article. For example, in U.S. Pat. Nos. 2,706,902 and 2,982,454 combination devices for personal use are disclosed that have sheathes in which both a key as well as a nail file and a knife blade may be positioned. U.S. Pat. No. 4,317,638 discloses a holder for holding both a key ring and a writing pen. In U.S. Pat. No. 4,312,128 a device is taught for attaching a key ring or key chain to a cutting blade.
Although some of the just described devices have been capable of coupling together useful tools, their structural shapes have been quite different from those of conventional pocketknives. For example, they have typically been of simple, light weight design having small blades of specialized shape and duty. Their blades have often been constructed to be detachable from the holder for use. They have typically had no interlock mechanism for holding their blades in either a sheathed or in an unsheathed position. Thus, their structure and form has been designed at a sacrifice of attributes attributable to conventional pocketknife designs which today have reached a high degree of refinement. Therefore, it is seen that a need remains for a pocketknife of a generally conventional construction that may be used without blade detachment and to which a key ring may be releasibly fastened securely and with facility. It is to the fulfullment of such need that the present invention is primarily directed.